Abrasive covering for sanders



March 19, 1929. J. F. A. DAVIS 1,706,351

ABRASIVE COVFRING FOR SANDERS 1 Filed d ly 2, 1926 TTEIR E5: 1" NH Patented Mar. 19, 1929.

UNITED STATES 1,706,351 PATENT oFF cE.

JOHN F. A. DAVIS, OF WENHAM, MASSACHUSETTS, ASSIGNOR TO AMERICAN GLUE COMPANY, OF BOSTON; MASSACHUSETTS, A CORPORATION OF -MASSACHUSETTS.,

ABBASIVE COVERING FOR SANDERS.

Application filed July 2, 1926. Serial. No. 120,207.

The present invention relates to an improved abrasive'covering for the wheel of a sanding machine, which wheel is rotated during the operation of the machine for sanding purposes.

The abrasive covering used forthis purpose usually consists of a base sheet of paper 01' other suitable fibrous material more or less flexible, and the abrasive is fixed to it by means of glue,-or other binder of suitable character, to form a bond between it and the paper and securely hold in place the abrasive embedded within it.

The abrasive covering is secured to the wheel by wrapping it around the wheel and securing its ends within a slot cut lengthwise in the wheel. This slot is a relatively nar row one and necessitates sharp bends being formed in the covering adjacent its ends to permit their entering the slot. Such benda ingof the covering has given great trouble by causing either a fracture in the binder which secures the abrasive to the base sheet oripaper or a fracture in both the binder and the paper or at least a weakening of the paper at the point or points of the bends. In case the binder only is fractured the tendency is for it during the operation of the wheel to strip from the paper, the stripping beginning at the point of the fracture. In case there is a fracture in both binder and paper or weakening of the paper then there is a tendency for the paper itself to strip from the wheel. Either or both of these diflieulties may arise before the usefulness of the abrasive covering has become in any way impaired and accordingly causes great annoyance, to

say nothing of loss of time. possibility of in- I to jury to the work and loss of the covering.

The objectofthe invention is to (Wercome these difliculties, and I havefound that they may be overcome by a fixing 9f the covering before its attachment to the sanding wheel, and this by a fixing, as will later be explained, of the binder portions of the covering which lie adjacent the respective ends thereof and in which portions the bends occur where the endsof the covering are turned to fit within a the slot in the sanding wheel on applying the covering thereto.

The invention can best be seen and understood by reference to the drawings in which- Figure 1 is a side elevation of the improved covering.

Fig. 2 is a plan.

Fig. 3'is an end elevation of the covering curled in position to be applied to the Wheel or roll of a sander.

Figs. 4 and 5 are views partly in section and partly in side elevation illustrative diagrammatically of one method of treating the covering for overcoming the difficulties sought to be overcome, in accordance with the object of the invention.

Referring to the drawings 1 represents the improved abrasive covering for the sanding Wheel. It comprises a base sheet 2 of paper or other suitable fibrous material and an abrasive-carrying adhesive binder 3 bonded at 4 to the surface of the base sheet or paper.

5, 5, represent the inturned ends of the covering which are the ends turned to extend into the slot of the sanding whee-l (not shown) and be there retained in the usual n'lanner,

The ends are turned in the general direction of the uncoated side of the covering and as the ends are rather abruptly turned, sharp bends are necessarily formed in the covering adjacent the ends which cause the difiiculties previously referred to.

According to the present construction the abrasive-earrying binder 3 in those portions 6, 6 of the covering adjacent its ends is fractured, by minute cracks relatively close together with extension generally crosswise the covering whereby the integrity of the binder along said portions of the covering is destroyed, butthe integrity-of the base sheet and that of the bond between the sheet and the binder is maintained along those portions. In other words,-the binder is so fractured or cracked that when the covering is applied to the sanding wheel and the portions adjacent 9 .its ends abruptly bent there will be no localized fracture or cracking of the binder as might cause it to break away from the sheet, or throw stress on the sheet, thereby either breaking or weakening it, inasmuch as the binder has already been so cracked as to prevent this. The cracking of the binder does not destroy thebond between it and the sheet nor does it affect the integrity of the sheet although it tends to give pliability to the sheet and impart a convexity thereto along those portions 6-6 thereof in which the cracks occur. This effect is obtained by mechanism illustrated in Figs. 4 and 5. A roll 7 of elas tie material such as rubber is provided and l the roll is rotatable in the direction indicated by the arrowthereon. Arranged adjacent the roll is a plunger 8 havin a curved end 9 which engages the roll. he plunger is backed by a strong spring 10 the tension of which when the spring is released throws the plunger in the direction of the roll and causes its curved end to press into the roll substantially as shown in Fig. 5 forming a rounded depression therein. Just beyond the point where the curved end of the plunger meets the roll. On the release of the spring the.

plunger will force the coveringehard against the roll and will efiect a bend in the covering as the curved end of the plunger presses into the roll. As the roll is rotating such curving or bending of the covering will continue from -the point of the initial application of the plunger to the nearest end of the covering in asmuch as the rotation of the roll will cause the covering to be thrown out from between theroll'and the plunger. The effect is that the binder will be fractured by minute cracks relatively close together with extension generall crosswise the covering in those portions which have-been thus bent but without inj uring the base sheet or paper or destroying the bond between the binder and the paper inasmuch as the paper and the binder are being held hard pressed against the yielding surface of the roll while the binder is being fractured. The fracturing of the binder tends to impart a convexity to the ends of the covering along the portions 6, 6 thereof in which the binder is fractinred By thus fracturing the binder at the ends of nvcasei ering is applied to thewheel no strain will come upon the binder as will cause it to strip from the base sheet or paper, nor will there be any fracturing or weakening of the base sheet, the minute cracking of the binder at the points where the bends occur eliminating all such strain upon the base sheets as might otherwise tend to break it or at least weaken it,

By the term fsanding wheel as herein used is broadly meant any wheel or drum to which an abras1ve covering is applied and the ends secured by fitting within; a slot in the wheel or drum.

Having thus fully described my invention, I'claim and desire to secure by Letters Patent ofthe United States 1. An abrasive covering for a sanding wheel in which the ends of the covering are attach-- able to the wheel, comprising a base sheet of ifibrous material and an abrasive carrying adhesive binder bonded to the sheet, the binder along those portions of the abrasive cover" ing adjacent to the respective ends thereof. and prior to the attachment of the abrasive covering to the wheel being fractured by minute cracks relatively close together with extension generally crosswise the covering whereby the integrity of the binder along said portions of the covering is destroyed but the integrity of the base sheet and that of the bond between the base sheet and binder along said portions of the covering is maintained. 2. An abrasive covering for a sanding wheel in which the ends of the covering are attachable to the wheel, comprising a base sheet or fibrous material and an abrasive carrying adhesive binder bonded to the sheet, the hinder alon those portions of the abrasive cover ing ad acent to the respective ends thereof and prior to the attachment of the abrasive covering to the wheel being fractured by rninute cracks relatively close together with extension generally crosswise the covering. whereby the integrity of the binder along said portions of the coveringis destroyed and convexity imparted ,to said portions of the; covering, but the inte ity of the base sheet and that of the bond liletween the sheet and binder along said portions of the covering is maintained.

JOHN F. A, DAVIS 

